According to Euler's column theory, the crippling load for a column length (l) hinged at both ends, is

• A. <img src="/_files/images/mechanical-engineering/strength-of-materials/121-406-1.png">
• B. <img src="/_files/images/mechanical-engineering/strength-of-materials/121-406-2.png">
• C. <img src="/_files/images/mechanical-engineering/strength-of-materials/121-406-3.png">
• D. <img src="/_files/images/mechanical-engineering/strength-of-materials/121-406-4.png">